Lights out for animals this Earth Hour

Landmarks such as the Sydney Harbour Bridge will turn off their lights for Earth Hour on Saturday.Image: AAP

Australians are being urged to do their part for wildlife struggling from the impacts of climate change by switching off the lights this Earth Hour.

Millions of Australians are expected to turn off the power on Saturday for an hour from 8.30pm as part of a global movement to bring attention to climate change.

Climate Council scientist Lesley Hughes has urged people to take part and tackle climate change before it's too late.

"The survival of Australia's unique ecosystems is at stake and we are already seeing animals being decimated by drier and hotter conditions," Professor Hughes told AAP in a statement on Thursday.

This Earth Hour will also shine a light on biodiversity loss after millions of fish died in the Darling River in western NSW, thousands of flying foxes dropped dead in Cairns and koala populations decreased across NSW and Queensland.

For every person who signs up for the movement, a message will be sent to federal politicians calling for Australia to get back on track when it comes to meeting the UN Paris climate agreement.

Environmental group WWF expects more than 250,000 messages will be sent to politicians urging them to take action.

"For this year's Earth Hour, we are shining a torch on how climate change is killing our animals, and destroying our landscapes and oceans," WWF's Darren Grover told AAP in a statement.

Landmarks such as the Sydney Opera House and Sydney Harbour Bridge will turn their lights off for one hour during the event.